[T-Mobile, Samsung Galaxy SIII] rawdaddymagraden:
Hey Guys,

So After all of the recent questions and concerns I have seen and answered, I have decided to make a thread to help users understand the new file structure of android 4.2.x. I hope this will help those of you with questions and concerns and make for a smoother transition from 4.1.x and touch wiz roms.

I will break this into three categories........

First I will explain what the file system is and why it is present and how it affects you......

Second is if you haven't yet but are planning on making the jump to 4.2.x.

Third will be if you have already made the jump without doing your homework. (For those of you wondering where your files are, wondering why your sd card was formatted, or cant find your recovery backups..... This section is for you!!)

Section 1.)

What is the new file system and what the hell is this /0 folder?

With Android 4.2, Google introduced multiple users as a new feature. In order to accommodate multiple users, Google is now giving each user their own folder for storage. What happens is 4.2 uses an emulator to make different users and uses the /0 folder as the default users storage on the sd card. It doesn't recognize anything on the root of the sd card only whats in /0. To support multi-user capabilities this will be the norm... for each user, there will be a sequentially numbered folder in /data/media (/data/media/0, /data/media/1)...

And for each user, within Android, this will be symlinked to /sdcard & /storage/sdcard0... for user 1, /sdcard = /storage/sdcard0 = /data/media/0... for user 2, /sdcard = /storage/sdcard0 = /data/media/0...

These are emulated storage points... /data/media/0 = /storage/emulated/0, /data/media/1 = /storage/emulated/1

Without root access, each user will just see /sdcard/ and will not be able to access the other emulated storage points...

In the recovery mode, however, /sdcard is mapped to /data/media which is why you need to navigate to the "0" folder to see your files!

So in order to access your internal storage files they will be in data/media/0. So for example to access the backup location In titanium backup after you flash navigate to data/media/0/TitaniumBackup. (Thanks to ktetreault)

That being said, If you already flashed a 4.2 rom without preparation, your files aren't lost they are just inaccessible they are just not in the proper place for 4.2 to see them.

So now that we have all the technical stuff out of the way...... Lets get into how to either prevent or fix this issue.

Section 2.)

Preparing to flash a 4.2 rom from a touch wiz rom or an aosp 4.1.x based rom.

Okay, so you have touch wiz or aosp 4.1.x of some sort and your ready to try out the goodness of 4.2?

First backup your ext sd card to your pc or if a pc is unavailable (and your willing to take a risk) use a file explorer on your phone such as Es file explorer from the market to transfer the contents of the ext sd card to your internal sd card. I highly suggest avoiding using the phone as some hiccups can occur. I have done it successfully myself but have heard others who have lost their files during transfer because they left the app while it was transferring. If you do use this method DO NOT LEAVE THE APP UNTIL THE FILE TRANSFER IS COMPLETE.

Second Format your ext sd card so we have a clean slate to work with as this will help tremendously to avoid any headaches.

Third Install the latest recovery of your choice. The reason for this is that the older recoveries are not updated for 4.2 and will continuously create a new /0 folder every time you flash a new rom. Follow the instructions to install in the applicable thread.

Thanks to naddict for posting the links.... These are all flashable zips thru recovery

TWRP 2.4.1.0 - http://d-h.st/9cL

CWM 6.0.2.3 - http://d-h.st/jbT

CWM Touch 6.0.2.3 - http://d-h.st/8A9

Fourth Flash the 4.2 rom of your choosing per the instructions of the developers OP in their thread.

Set your phone up as usual and then restore the files from your backup on your pc or move them back from the internal sd card using es file explorer again. Keep in mind that the /0 folder is your new sd card storage. Now you are good to go and enjoy the new features and benefits of 4.2 and not have to search for your files :good:

Section 3.)

Okay so you got overly excited and flashed a 4.2 rom........ OMG!!! All my files are gone!!!! I can't restore any backups and all my precious files have disappeared!! Why was my sd card formatted?????

Relax.... Your files didn't go any where they are exactly how you left them you just can't see them.....

I will walk you thru 4 easy steps to get your files back and put you back on track.

First Make sure you have the latest recovery of your choice. If needed refer to the links posted in section 1. If you don't do this you will see a duplicate /0 folder created every time you flash a new 4.2 rom.

Second You won't be able to find your backups thru recovery. The easiest method I found is to download any touch wiz rom. Wipe your phone completely and then flash the touch wiz rom you downloaded. Reboot and go thru the setup and what not.

Third Now install es file explorer or the app of your choice. Next copy everything from the root of the sd card into the /0 folder that 4.2 had created oh so nicely for you.

Fourth Reboot into recovery and re-flash the 4.2 rom you began with. After going thru the initial rom setup you will see that are of your files are back intact and ready for you to access.

Hopefully this has helped those of you with questions and concerns about upgrading to 4.2.x. If i missed anything please feel free to let me know and ill include it here or address any further questions.

Thanks to:

Sundawg of TBD

Koush Of CWM

Team Win

And All of the devs on xda

Hope I have helped if so feel free to press thanks!!